As for Mr. Baghdadi, the Defense Department has no concrete evidence of whether he is still alive, Col. Ryan Dillon, a spokesman for the American-led coalition that is fighting the Islamic State, told reporters on Friday from Baghdad.
“That said, we don’t have any concrete evidence on whether or not he’s dead, either,” Colonel Dillon said of Mr. Baghdadi, who has been the subject of a three-year manhunt.
Since the American-led bombing campaign against the Islamic State began in August 2014, reports of Mr. Baghdadi’s death have repeatedly surfaced. None have turned out to be true.
The latest foray into figuring out whether the Islamic State leader is dead or alive began June 16, when Russia’s military — which is also bombing the Islamic State in Syria — said it was looking into whether one of its airstrikes in the Syrian desert had killed Mr. Baghdadi, the self-declared caliph of the Islamic State. In a statement, the Defense Ministry said the Russian Air Force had struck a meeting of Islamic State leaders on May 28 outside Raqqa, Syria, the group’s de facto capital, possibly killing Mr. Baghdadi.
This week, Russia upgraded its assessment, as the deputy foreign minister, Oleg V. Syromolotov, said that Moscow was increasingly certain that Russian warplanes had killed Mr. Baghdadi three weeks ago.
Throughout it all, American defense officials have maintained that they have no proof that the Islamic State leader is dead. They said they were reviewing reports from May 28 and subsequent days for clues, but pointed out that Mr. Baghdadi has not been heard from publicly since November, when the Islamic State released a blistering audio recording in which he urged forces to remain firm in the face of the American-backed Iraqi offensive in Mosul. So the fact that he has not popped up publicly since May 28 does not necessarily mean he has been killed.
But on Friday, Colonel Dillon seemed to inch — ever so slightly — in the direction that Mr. Baghdadi may be dead. “We certainly know that if he is still alive, we expect that he is not being able to influence what is currently happening in Raqqa or Mosul or over all,” he told a Pentagon briefing, “as they continue to lose their physical caliphate.”
Military officials insisted they did not mind whether the Russians killed him and not the American-backed coalition. If, that is, he actually is dead.